<template>
  <div>
    <router-link tag="div" to="/" class="header-abs" v-show="showAbs" >
        <div class="iconfont header-abs-back">&#xe665;</div>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
        <router-link to="/">
            <div class="iconfont header-back">&#xe665;</div>
        </router-link>        
        景点详情
    </div>
  </div>
</template>
<script>
export default {
  name: 'DetailHeader',
  data () {
      return {
          showAbs: true,
          opacityStyle: {
              opacity: 0
          }
      }
  },
  methods: {
      handleScroll () {
        // 兼容性写法
          const top = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset
          if(top > 60 ) {
              let opacity = top / 140
              opacity = opacity > 1 ? 1 : opacity
              this.opacityStyle = {
                  opacity
              }
              this.showAbs = false
          } else {
              this.showAbs = true
          }
      }
  },
  // activated () {
  //     window.addEventListener('scroll', this.handleScroll)
  // },
//   离开页面的时候销毁事件监听，防止其他页面受到影响
//   deactivated () {
//       window.removeEventListener('scroll', this.handleScroll)
//   }
  mounted () {
      window.addEventListener('scroll', this.handleScroll)
  },
  destroyed () {
      window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>
<style lang="stylus" scoped>
@import '../../../assets/styles/var.styl';

.header-abs {
  position: absolute;
  left: 0.2rem;
  top: 0.2rem;
  width: 0.8rem;
  height: 0.8rem;
  line-height: 0.8rem;
  text-align: center;
  border-radius: 0.4rem;
  background: rgba(0, 0, 0, 0.8);
}

.header-abs-back {
  color: #fff;
  font-size: 0.4rem;
}

.header-fixed {
  z-index: 3;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  overflow: hidden;
  height: $headerHeight;
  line-height: $headerHeight;
  text-align: center;
  color: #fff;
  background: $bgColor;
  font-size: 0.32rem;
}

.header-back {
  position: absolute;
  top: 0;
  left: 0;
  width: 0.64rem;
  text-align: center;
  font-size: 0.4rem;
  color: #fff;
}
</style>